Electronic devices, such as cellular telephones, cameras, and computers, commonly use a lens module in conjunction with an image sensor to capture images. Many imaging systems employ autofocus methods and various signal processing techniques to improve image quality by adjusting the position of the lens relative to the image sensor.
Autofocus systems generally employ an actuator to move the lens to an optimal position to increase the image quality. Many electronic devices utilize low-noise linear motion, such as linear actuators, to facilitate autofocus. Due to the mechanical properties of the linear actuator, the operation of the actuator is governed by the Lorentz Force principle. When a constant current is applied to the actuator, a constant force is created as well as an induced voltage that is proportional to the velocity of the actuator. In some cases, external forces or control operations may generate resonance vibrations in the actuator, which affect the settling time of actuator. The normal mode of operation of the actuator, however, is not designed to directly stop or suppress the resonance vibrations. Therefore, the settling time of the actuator may be greater than desired.